An image display devices such as a liquid crystal display (LCD), a plasma display (PDP), an electroluminescent display (OELD or IELD), a field emission display (FED), a touch panel, and an electronic paper, has an optical layered body including a polarizing device provided on a display screen side of an image display panel, and an antireflective topmost surface with hard coatings.
Films formed of cellulose esters such as triacetyl cellulose have been conventionally used as light transmissive bases of such optical layered bodies. Cellulose esters hardly influence the display quality of image display devices because of their low retardation values and have appropriate permeability. Accordingly, such a use is based on an advantage that moistures left in a polarizing device in the production of a polarizer formed of an optical layered body can be dried through the optical layered body. In addition, comparative inexpensiveness of cellulose ester films also contributes to the use.
Cellulose ester films, however, have poor heat and humidity resistance. Use of a hard coating film as a polarizer protective film in a high-temperature and high-humidity environment problematically lowers performances of a polarizer such as polarization and hue control.
To solve such problems of cellulose ester films, use of a general-purpose film that is commercially available or easily produced by a simple method, as a base of an optical layered body has been desired. For example, use of polyester films such as polyethylene terephthalate films, instead of cellulose ester films, is now considered (see Patent Literature 1).